<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        ul{
            display: flex;
            flex-wrap: wrap;
            width:100%;
        }
        li{
            background-color: aqua;
            border:1px solid red;
            list-style: none;
            box-sizing: border-box;
        }
        @media screen and (min-width:992px){
            .box{
                background-color: red;
            }
            li{
                width:25%;
            }
        }
        @media screen and (max-width:991px) and (min-width:768px){
            .box{
                background-color: blue;
            }
            li{
                width:50%;
            }
        }
        @media screen and (max-width:767px){
            .box{
                background-color: pink;
            }
            li{
                width:100%;
            }
        }
    </style>
</head>
<body> 
    <!-- 一款代码，在不同的设备上展示不同的效果
         简单的网站(pc 移动端 ipad)---核心 媒体查询

         响应式开发--bootstrap
     -->

     <!-- <div class="box">111</div> -->
     <ul>
        <li>111</li>
        <li>222</li>
        <li>333</li>
        <li>444</li>
     </ul>
</body>
</html>